The use of ultrasound to obtain images for diagnostic puposes of the interior scanned sectors of patients has been steadily becoming more sophisticated. One of the improvements to ultrasonic diagnostic imaging has been brought about by the use of probes that are inserted into cavities in the body to obtain images of various parts that are juxtaposed to or located within such cavities. Such probes, for example vaginal probes, are severely limited physically by the human body so that, for practical purposes, the probe can only be moved by rotating it around its longitudinal axis. This severely limits the orientation of the scanned sectors.
Therefore, within the spatial limitations of the probe itself, those skilled in the art have been attempting to increase the orientations of the scanned sectors or views that can be obtained by movement of the transducer within the probe. It is relatively simple to place the transducer in such a probe and obtain scans of a single plane or even a few planes. However, it is difficult to design such a probe wherein the transducer will be able to scan a multiplicity of planes that are selected by the operator in an effective manner providing control and repeatability.
In general, the ultrasonic imaging systems comprise a console and a multiplicity of probes individually dedicated to the various specific diagnostic tasks. Probes are plugged interchangeably into a socket or sockets on the console for use in transmitting ultrasonic signals and receiving echoes of these ultrasonic signals. The echoes are sent back to the console for data processing to obtain images from the echoes. The probes detect data used for the reconstruction of the image of a section or a region in the patient's body. The probes include a transducer that converts electrical energy into ultrasound energy and the echoes of the ultrasound energy back into electrical energy.
In general the transducers oscillate (or reciprocate about a fixed axis stationary in the probe. The angle of the scan or of the reciprocating motion is about 110 degrees. That is, a scan sector of 110 degrees is the normal fan shaped field of view in ultrasonic examination. With hand held probes, the probe is brought into contact with the part of the body closest to the region of interest. The plane of the sector is selected by the position of the hand held probe.
More recently, the demand for improved quality images of the organs located inside the body, away from the surface or being in the position where there are acoustically interfering sections of the body, has brought about the utilization of what are herein referred to as endocavital probes. Such probes are inserted into an interior cavity of the body and obtain the data directly from the interior cavity of the body.
The end of the probe usually has a bulbous section which contains the transducer and enables reciprocating motion of the transducer. The end of the bulbous section also contains a viewing window through which the ultrasonic signals and echoes are transmitted and received.
The bulbous section is mounted on an elongated stem which connects a handle to the bulbous section. The handle, in a preferred embodiment, houses the drive motor and control elements. Due to the natural size constraints of the body it is necessary to miniaturize the endocavital parts of the probe. For example, the bulbous section and the stem must be kept radially as small as possible.
Notice that the selection of the sector scanned by the transducer of the probe in the externally applied probes is not limited; whereas in the endocavital probe the sector selected is severely limited and in fact it can be varied only by the rotation of the probe about the stem axis. Thus in the prior art endocavital probes the scan of a sector is accomplished when the transducer reciprocates and to scan additional sectors, the stem is rotated.
In effect, then, there are two types of volumes that are readily obtainable with the presently available endocavital probes. They are a cone shaped volume and a ring shaped volume of revolution. When the center line of the sector scanned by the transducer coincides with the stem axis then rotation of the probe about the stem axis will result in obtaining a cone shaped volume. When the axis of the scanned sector is at right angles to the axis of the stem, then rotation of the probe will result in a ring shaped volume.
To effectively use endocavital probes, it is necessary that they are capable of scanning in more than two planes. Thus, for example, besides locating an organ in the endocavital region, it is helpful for diagnostic purposes, to be able to determine the volume of the organ. This requires scanning in more than one plane and it further requires that the planes that are scanned are not necessarily at right angles to each other but at a multitude of angles to each other between 0 and 90 degrees.
Thus, those skilled in the art are looking for effective methods of obtaining multi-planar images using endocavital probes.